06-07-2015, 11:58 PM
I have been sorting out the dodgy 7A26.
It had a very intermittent loss of all gain on all ranges on channel 2 while channel 1 was all right.
You can see all the tool marks where the twiddler has been swapping the chips around to try and clear the fault.
I did many in circuit tests with a diode tester including the input junctions on the bipolar chips. They are transistor arrays. I eventually got to the wires and switches and found that the channel 2 invert switch was totally open circuit. It is a bit disappointing for Tektronix being just a little slider switch.
With twiddler evidence and the trace moving when some switches are operated indicates that the twiddler has been at the pots too.
Time to go through the calibration procedure now.
It had a very intermittent loss of all gain on all ranges on channel 2 while channel 1 was all right.
You can see all the tool marks where the twiddler has been swapping the chips around to try and clear the fault.
I did many in circuit tests with a diode tester including the input junctions on the bipolar chips. They are transistor arrays. I eventually got to the wires and switches and found that the channel 2 invert switch was totally open circuit. It is a bit disappointing for Tektronix being just a little slider switch.
With twiddler evidence and the trace moving when some switches are operated indicates that the twiddler has been at the pots too.
Time to go through the calibration procedure now.
